Art of grinding annular surfaces



July 29, 1947. J. w. ALSDORF ART OF GRINDING ANNUL'AR SURFACES FiledMarch 25, 1944 4 Sheets-Sheet l July 29,1947. J. w. ALSDOYRF. 2,424,544

ART OF GRINDING ANNULAR SURFACES Filed March 25, 1944 4 Sheets-Sheet 2July 29, 1947. J. ALSDORF 2,424,544

ART OF GRINDING ANNULAR SURFACES Filed March 23, 1944 4 Sheets-Sheet 3July 29, 1947. J. w. AL'SDORF 2,424,544

ART OF GRINDING ANNULAR SURFACES Filed March 25. 1944 4 sheets-shet 4Patented July 29, 1947 ART OF. GRINDING ANNULAR SURFACES James W.Alsdorf, Winnetka, Ill., assignor, by

mesne assignments, to Cory Corporation, a corporation of DelawareApplication March 23, 1944, Serial No. 527,744

This invention which relates generally to the grinding of annularsurfaces is concerned both with an apparatus and a method therefor. Inparticular the herein disclosed apparatus and method have specialutility in the grinding of an annular sealing surface upon the upperbowl of a vacuum coffee brewer which is commonly produced from borosilicate glass. Problems encountered in the grinding of such objectsinclude (1) the high degree of precision that is required, (2) theextremely hard nature of the work that is to be treated, and attainmentof (3) speed and uniformity in each operation so that the cost may beheld to a minimum.

With the aim of attaining these and other bjectives, I have devised asimple and inexpensive apparatus for carrying out this invention, asuggestive embodiment being illustrated in the drawings in the mannerfollowing:

Figure 1 is a view in horizontal section, taken on line l l of Fig. 2,showing in plan the relationship of the several grinding wheels, alsothe drives therefor; Figs. 2 and 3 are vertical sections, taken on line2-2 of Fig. 1, showing the work holding means in different positions;Fig. 4 is a detail in section, taken on line 4-4 of Fig. 2; Fig. 5 is adetail in elevation, taken from line 5-5 of Fig. 2; Fig. 6 is a detailin section, taken on 5 Claims. (01. 51-431) line 6-5 of Fig. 2; and Fig.'7 which is an inverted view in plan of the upper bowl of a coffeebrewer shows the annular surface on which grinding is performed.

As shown, the apparatus comprises a bed 5 supported upon legs 6, with apair of motors 1 and 8 disposed opposite adjacent sides of the bed atpoints therebelow. Resting upon the bed is a pan 9 having in its bottoma more or less central opening and three other grouped-about openingsthrough all of which, and the bed as' well, are extended certainvertical shafts as will now be explained. The central shaft l5 which issplined for axial movement relative to a driving pulley it near itslower end extends upwardly through a suitable bearing I! having a flangel8 which overlies the bed to rest thereupon. In like manner theremaining three shafts 20, 2|, and 22 which are disposed substantiallyequidistant from each other and from the central shaft, are eachextended vertically through lower bearings 23 affixed to the bed andthrough upper bearings 24 which rest on the pan bottom, these threeshafts carrying at their lower ends pulleys 25 at elevations which aredesirably staggered. Belts 26 extending over these several pulleys 25and a multiple pulley 2'! on the shaft motor 75 provide a powertransmission which will produce a concurrent unidirectional rotation ofall three shafts 2|], 2|, and 22. Between the pulley It on the centralshaft and the other motor 8 there is also a transmission belt 28 wherebyto drive this shaft independently of the others both as to speed anddirection of rotation.

Afiixed to one side of the bed is a bracket 29 provided with a verticalguideway 36 wherein is slidably supported a framework comprising a post3| from which is extended a tension adjusting device for holding thework under axial pressure in a rotating chuck. As shown, this deviceincludes a fixed lateral arm 32 in pivotal connection with one end of alink 33 whose opposite end is pivotally joined to an adjusting lever 34extending in a generally horizontal direction over the pan. Theframework also comprises a second fixed arm 35 which extends laterallyfrom the post to overlie the pan substantially in line with the centralshaft [5, this arm being provided with a bearing 36 through which avertical thrust rod 31 is slidably supported. This rod which is coaxialwith the shaft l5 extends upwardly to support thereon a fixed collar 38receiving thrust from the lower end of a compression spring 39 which iscoiled around the rod, the upper spring end engaging with a collar 49that is pivotally joined at 4| to a yoke 42 upon the lever 34 (see Fig.4). A fixed bracket arm 43 also forming part of the framework isextended laterally from the post 3] at a point near its upper end andcarries a top bearing 44 for the thrust rod 31, and just above thisbearing the rod may be fitted with a stop collar 45 by which to limitits downward movements.

Extending upwardly from the fixed arm 35 proximate to the pressure rodis a bar 46 carrying a bearing 41 wherein is rookably mounted a shaft 48operable by a crank pin 49. A grooved 'eccentric wheel 59' is carriedfast upon this handle pin from the eccentric wh'eel, whenever the leveris to be swung upwardly to the position indicated by the dotted lines inFig. 3, the pivotal connection 4! between the yoke 42 and adjustinglever being slidable, as required, for this purpose. In any such upwardmovement the spring 39 contributes an assisting force. Desirably theeccentric is rotated preliminarily to the dotted line position of Fig. 3so as to minimize the manual force, counter to that of the spring,require for disengagement of the handle pin, and conversely, upon returndownward swinging movement of the lever, the eccentric should remain inthis same position until after re-engagement of the handle pin with theeccentric has been effected. The spring will then be under tension, butnot so much as after the eccentric has been rocked to the full lineposition of Figs. 2 and 3.

Returning now to the axially movable, power driven central shaft I5whose upper end is extended through the bearing l1 and pan bottom, Iprovide also an upper bearing therefor which comprises an arm 55extending fixedly from the framework post 3| and formed at its outer endinto an elongated cup 56 for accommodation of roller bearings 5'!rotatably supporting a chuck which may comprise a hollow cylindricalhead 58 that is carried fast on the upper end of the shaft with a thrustcollar 58 affixed thereto in engagement with the bottom end of the cup.Above the cup the head is formed with a flange 60 from which depends askirt 6| in overlapping relation to the upper edge of the cup, wherebyto prevent ingress of grit or foreign matter to its interior.

At its top the head is formed with a cylindrical boss 62 around which isa shell 63 extending upwardly therebeyond to confine in place aresilient or yielding seat 64 having a central opening in communicationwith the interior of the head. Between the cup bottom and pan bottom Imay extend an extensible boot 65 having one end affixed to each wherebyto prevent ingress of grit or foreign matter to the lower bearing IT.The parts just described, viz. the head 58, shell 63 and seat 84,constitute the principal elements forming the chuck wherein the objectis supported.

The post 3| which has capacity for limited vertical sliding movements inthe guideway of its supporting bracket is in pivotal connection at 10with a control lever H which is fulcrumed at 12 upon the upper end of alink 13 having a pivotal connection at 14 with the bracket 29. Near onelever end beyond its fulcrum point is a weight 15, the lever through itsopposite end region being somewhat laterally offset (see Fig. 6) toclear a head 16 which is mounted at the lower end of the thrust rod 31for free rotation thereon. In the path of movement of the control leveris the trigger I! (or other actuating element) of a micro-switch 18 inelectrical connection 19 with the motor 8 by which the shaft I5 isdriven, the arrangement being such that with such downward movement ofthe control lever H, counter to the force exerted by its weight 15, theswitch will be closed to cause rotation of the central shaft and thehead supported thereby, and with each upward movement of the controllever to produce a cessation of such rotation.

Typical of the .work upon which grinding may advantageously be performedwith the apparatus herein disclosed is the upper bowl for a vacuumcoffee brewer. Such an object may take the form of a bowl 88 having onits bottom a raised annulus 8| to the inside of which the bowl wallscontinue on downwardly to provide a hollow base forming a well 82 whosebottom, in the center region, is downwardly flared at 83 to join with adepending hollow stem 84 (see Fig. '7). The annulus of such an upperbowl is rested upon the seat of a complementary lower bowl when thecoffee brewer is assembled for operation. Such an annulus and the seatwhereon it is rested sh'ould cooperate to establish an effective sealbetween them independently of any extraneous means, and to accomplishthis the contacting surfaces are ground and then lapped to the degree ofprecision necessary for attainment of this objective. The grindingoperation may be expeditiously and accurately performed by positioningthe work upon the head 53 with its stem extending down into the interiorthereof. The base or bottom of the bowl well will then rest upon theresilient seat 64 whose central opening is flared in conformity with theflare 83 of the bowl bottom whereby to center the work accurately inplace. Inside the bowl is then placed a cylindrical block 85 of wood orthe like, the bottom end of this block being formed with an axial bosswhich enters slightly into the well. In this way the block is centeredwithin the bowl so as to bear evenly and continuously at everyperipheral point directly over the annulus which is to be ground.

The top end of this block extends to a point about even with the top ofthe bowl so as to receive engagement from a head block 86 which issupported upon the underface of the rod head 16. With such anarrangement of parts, the Work, after being coaxially fitted into thehead seat 64, is pressure held thereon and thereby positively lockedthereto so as to rotate therewith in response to downward movement ofthe control lever H which also produces a like movement of the post 3|;and in this latter movement the entire tension adjusting device alsoparticipates so that the thrust rod 31 is advanced toward the work toexert thereon a yielding force whereby to hold the work firmly againstthe chuck seat.

When the work i positioned in the chuck for rotation therewith, theraised annulus 8| will lie just beyond the periphery of the shell 63 ina position of exposure for engagement concurrently with flat annulargrinding surfaces 98 which are extended slightly above the top surfacesof grinding wheels 9| of disk form (three being the number shown)mounted respectively upon the shafts 20, 2| and 22 to be driven thereby.Adjacent each grinding wheel is a holder 92 for containing a supply offinely divided abrasive material in a pasty mass upon which water maydrip from a valve pipe 93 to assure a more or less continuous feed ofthe abrasvie material to the several grinding surfaces which engage thework when performing a grinding operation upon its raised annulus.

During operation of the machine the three grinding wheel will remaincontinuously in motion, say at about 700 R. P. M., rotating preferablyall in the same direction. The spacing and grouping of these wheels (seeFig. 1) is such that each presents only a small arc of its grindingsurface in contact with the work annulus to be operated upon, yet thecombined areas thereof are a substantial part of the work annulus. Whenthe work is to be placed in the chuck, which is then motionless, theparts will occupy positions as indicated in Fig, 3, the tension lever 34being raised to its uppermost position (shown in dotted lines) to permitlifting of the thrust rod 3! in response to expansion of the spring 39.The'rod head 16 and head block 85 are then moved away from the chuck .adistance sufficient for placement of the work therein. The next step isto apply pressure axially of the work to hold it firmly in its seatWithinthe chuck. This involves a down pull on the tension lever to thepoint of positioning its handle pin :l beneath the eccentric wheel sothat the spring 3.9 may be placed under compression to exert its forceagainst the thrust rod ti; and if the eccentric wheel be thereafterrotated to anopposite position the tension of this spring, and inconsequence th pressure exerted thereby, will be substantially increased.

Up to this point the post 3i, together with all the mechanism supportedthereby, is sustained in an upper position by the counter weight I5 onthe control lever ll. The last step is to depress the free end of thislever thereby (1) closing the switch 18 to start operation of the motor8 and rotation of the chuck (at a speed of perhaps 400 R. P. M.) withthe work positioned therein, and (2) lowering the work, whilepressure-held c0- axially in the revolving chuck, to a position ofconcurrent engagement with the coplanar grinding surfaces of the threewheels 2!], 2|, and 22. During the ensuing few moments, while the workis maintained against these grinding surfaces in response to pressureexerted by the control lever, a grinding operation takes place. Theannulus of the work is uniformly and accurately treated at every pointin consequence of its rotation at a relatively slow speed in a directioncounter to the somewhat faster movement of the coplanar grindingsurfaces. This grinding operation is assisted by a slow, more or lesssteady, feed of fine abrasive material which is placed between thecontacting surfaces. A brief time is sufficient to perform the desiredgrinding after which the control lever is raised, the spring pressure isreleased, and the work is removed from the chuck which is then at astandstill.

It will be noted that the present mechanism utilizes (l) a chuck whichis axially movable to advance the work, while rotating, toward and fromthe relatively rotating coplanar grinding surfaces, and (2) a tensionadjusting device by which to hold the work with a yielding pressureagainst its yielding seat in the chuck. This is advantageous inasmuch asthe work is of a fragile nature and should be adequately protectedagainst jars and shocks at every stage of the grinding operation. Notonly is the work positioned against a seat that is yieldable within thechuck, but it is held against this seat in response to a yieldablethrust forcethat is axially directed and maintained constant regardlessof the relative axial positions of the chuck and grinding wheels.

I claim:

1. For grinding an annular surface upon an object, an apparatus whichcomprises a group of closely spaced wheels having parallel axes andco-planar grinding surfaces, a chuck for the ob ject rotatable about anaxis parallel with those of the grinding wheels, a framework including amounting wherein the chuck is fixedly held, a support wherein theframework is held for sliding movement in a direction parallel to thechuck axis, a thrust rod coaxial with the chuck having freely rotatablemeans engageable with the object, means carried by the frameworksupporting the thrust rod for movement axially of itself, tension meansurging the rod axially toward the object, driving means for rotating thegrinding wheels, other driving means for the chuck including a pair ofaxially slidable transmission elements, and means for imparting slidingmovements to the framework whereby to advance the chuck-supported objecttoward and from the grinding wheels without affecting the force of thetension means urging the rod toward the object.

2. For grinding an annular surface upon an object, an apparatus whichcomprises a group of closely spaced wheels having parallel axes andco-planar grinding surfaces, a chuck for the object rotatable about anaxis parallel with those of the grinding wheels, a framework including amounting wherein the chuck is fixedly held, a support wherein theframework is held for sliding movement in a direction parallel to thechuck axis, a thrust rod coaxial with the chuck having freely rotatablemeans engageable with the object, means carried by the frameworksupporting the thrust rod for movement axially of itself, driving meansfor rotating the grinding wheels, other driving means for the chuckincluding a pair of axially slidable transmission elements, and meansfor imparting sliding movements to the framework whereby to advance thechuck-supported object toward and from the grinding wheels.

3. For grinding an annular surface upon an object, an apparatus whichcomprises a group of closely spaced wheels having parallel axes andco-planar grinding surfaces, a chuck for the object rotatable about anaxis parallel with those of the grinding wheels, a framework including amounting wherein the chuck is fixedly held, a support wherein theframework is held for sliding movement in a direction parallel to thechuck axis, a thrust rod coaxial with the chuck having freely rotatablemeans engageable with the object, means carried by the frameworksupporting the thrust rod for movement axially of itself, driving meansfor rotating the grinding wheels, other driving means for the chuck, andmeans for imparting sliding movements to the framework whereby toadvance the chuck-supported object toward and from the grinding wheels.

4. For grinding an annular surface on an object, an apparatus comprisinga main frame having a vertical guide, a vertically slidable framemounted in the guide, a vertical motor actuated shaft journaled in theslidable frame and carried by the same and provided at its upper endwith a chuck, a vertical thrust rod journaled in the slidable frameco-axially with said shaft and mounted for both sliding and rotarymovement, and provided at its lower end with means cooperating with saidchuck for gripping an object to be ground, closely spaced coplanargrinding wheels grouped around said shaft in position for grinding theobject held between the chuck and the thrust rod, means for locking thethrust rod in engagement with said object, and operating means forraising and lowering the slidable frame to carry the object into and outof engagement with the grinding wheels.

5. For grinding an annular surface on an object, an apparatus comprisinga main frame having a vertical guide, a vertically slidable framemounted in the guide, a vertical shaft journaled in the slidable frameand carried by the same, and provided at its upper end with a chuck, avertical thrust rod journaled in the slidable frame co-axially with saidshaft and mounted for both slidable and rotary movement and provided atits lower end with means co-operating with said chuck for gripping anobject to be ground, close- 1y spaced coplanar grinding wheels grouped 5around said shaft in position for grinding an object held between thechuck and the thrust rod, a locking device mounted on the slidable framefor holding the thrust rod in engagement with said object, said lockingdevice being provided with yieldable means engaging the thrust rod forexerting a predetermined pressure on said object, and. operating meansfor raising and lowering the slidable frame to carry the object into andout of engagement with the grinding wheels while the object is heldbetween the chuck and the thrust rod.

JAMES W. ALSDORF.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,973,150 Morgan Sept. 11, 1934492,095 Medart Feb. 21, 1893 493,294 Procunier Mar. 14, 1893 95,341Harper Sept, 28, 1869 1,799,109 Lyne Mar. 31, 1931 1,084,529 Bentzon eta1. Jan. 13, 1914 1,575,311 Bentzon Mar. 2, 1926 2,226,782 Sandberg Dec.31, 1940 975,408 Fry Nov. 15, 1910 386,738 Christie July 24, 1888737,811 Altenbaugh Sept. 1, 1903 1,607,292 Miller Nov. 16, 1926

